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tag: v1.8.2.1
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/*
* name-hash.c
*
* Hashing names in the index state
*
* Copyright (C) 2008 Linus Torvalds
*/
#define NO_THE_INDEX_COMPATIBILITY_MACROS
#include "cache.h"

/*
* This removes bit 5 if bit 6 is set.
*
* That will make US-ASCII characters hash to their upper-case
* equivalent. We could easily do this one whole word at a time,
* but that's for future worries.
*/
static inline unsigned char icase_hash(unsigned char c)
{
return c & ~((c & 0x40) >> 1);
}

static unsigned int hash_name(const char *name, int namelen)
{
unsigned int hash = 0x123;

while (namelen--) {
unsigned char c = *name++;
c = icase_hash(c);
hash = hash*101 + c;
}
return hash;
}

struct dir_entry {
struct dir_entry *next;
struct dir_entry *parent;
struct cache_entry *ce;
int nr;
unsigned int namelen;
};

static struct dir_entry *find_dir_entry(struct index_state *istate,
const char *name, unsigned int namelen)
{
unsigned int hash = hash_name(name, namelen);
struct dir_entry *dir;

for (dir = lookup_hash(hash, &istate->dir_hash); dir; dir = dir->next)
if (dir->namelen == namelen &&
!strncasecmp(dir->ce->name, name, namelen))
return dir;
return NULL;
}

static struct dir_entry *hash_dir_entry(struct index_state *istate,
struct cache_entry *ce, int namelen)
{
/*
* Throw each directory component in the hash for quick lookup
* during a git status. Directory components are stored with their
* closing slash. Despite submodules being a directory, they never
* reach this point, because they are stored without a closing slash
* in index_state.name_hash (as ordinary cache_entries).
*
* Note that the cache_entry stored with the dir_entry merely
* supplies the name of the directory (up to dir_entry.namelen). We
* track the number of 'active' files in a directory in dir_entry.nr,
* so we can tell if the directory is still relevant, e.g. for git
* status. However, if cache_entries are removed, we cannot pinpoint
* an exact cache_entry that's still active. It is very possible that
* multiple dir_entries point to the same cache_entry.
*/
struct dir_entry *dir;

/* get length of parent directory */
while (namelen > 0 && !is_dir_sep(ce->name[namelen - 1]))
namelen--;
if (namelen <= 0)
return NULL;

/* lookup existing entry for that directory */
dir = find_dir_entry(istate, ce->name, namelen);
if (!dir) {
/* not found, create it and add to hash table */
void **pdir;
unsigned int hash = hash_name(ce->name, namelen);

dir = xcalloc(1, sizeof(struct dir_entry));
dir->namelen = namelen;
dir->ce = ce;

pdir = insert_hash(hash, dir, &istate->dir_hash);
if (pdir) {
dir->next = *pdir;
*pdir = dir;
}

/* recursively add missing parent directories */
dir->parent = hash_dir_entry(istate, ce, namelen - 1);
}
return dir;
}

static void add_dir_entry(struct index_state *istate, struct cache_entry *ce)
{
/* Add reference to the directory entry (and parents if 0). */
struct dir_entry *dir = hash_dir_entry(istate, ce, ce_namelen(ce));
while (dir && !(dir->nr++))
dir = dir->parent;
}

static void remove_dir_entry(struct index_state *istate, struct cache_entry *ce)
{
/*
* Release reference to the directory entry (and parents if 0).
*
* Note: we do not remove / free the entry because there's no
* hash.[ch]::remove_hash and dir->next may point to other entries
* that are still valid, so we must not free the memory.
*/
struct dir_entry *dir = hash_dir_entry(istate, ce, ce_namelen(ce));
while (dir && dir->nr && !(--dir->nr))
dir = dir->parent;
}

static void hash_index_entry(struct index_state *istate, struct cache_entry *ce)
{
void **pos;
unsigned int hash;

if (ce->ce_flags & CE_HASHED)
return;
ce->ce_flags |= CE_HASHED;
ce->next = NULL;
hash = hash_name(ce->name, ce_namelen(ce));
pos = insert_hash(hash, ce, &istate->name_hash);
if (pos) {
ce->next = *pos;
*pos = ce;
}

if (ignore_case && !(ce->ce_flags & CE_UNHASHED))
add_dir_entry(istate, ce);
}

static void lazy_init_name_hash(struct index_state *istate)
{
int nr;

if (istate->name_hash_initialized)
return;
for (nr = 0; nr < istate->cache_nr; nr++)
hash_index_entry(istate, istate->cache[nr]);
istate->name_hash_initialized = 1;
}

void add_name_hash(struct index_state *istate, struct cache_entry *ce)
{
/* if already hashed, add reference to directory entries */
if (ignore_case && (ce->ce_flags & CE_STATE_MASK) == CE_STATE_MASK)
add_dir_entry(istate, ce);

ce->ce_flags &= ~CE_UNHASHED;
if (istate->name_hash_initialized)
hash_index_entry(istate, ce);
}

/*
* We don't actually *remove* it, we can just mark it invalid so that
* we won't find it in lookups.
*
* Not only would we have to search the lists (simple enough), but
* we'd also have to rehash other hash buckets in case this makes the
* hash bucket empty (common). So it's much better to just mark
* it.
*/
void remove_name_hash(struct index_state *istate, struct cache_entry *ce)
{
/* if already hashed, release reference to directory entries */
if (ignore_case && (ce->ce_flags & CE_STATE_MASK) == CE_HASHED)
remove_dir_entry(istate, ce);

ce->ce_flags |= CE_UNHASHED;
}

static int slow_same_name(const char *name1, int len1, const char *name2, int len2)
{
if (len1 != len2)
return 0;

while (len1) {
unsigned char c1 = *name1++;
unsigned char c2 = *name2++;
len1--;
if (c1 != c2) {
c1 = toupper(c1);
c2 = toupper(c2);
if (c1 != c2)
return 0;
}
}
return 1;
}

static int same_name(const struct cache_entry *ce, const char *name, int namelen, int icase)
{
int len = ce_namelen(ce);

/*
* Always do exact compare, even if we want a case-ignoring comparison;
* we do the quick exact one first, because it will be the common case.
*/
if (len == namelen && !cache_name_compare(name, namelen, ce->name, len))
return 1;

if (!icase)
return 0;

return slow_same_name(name, namelen, ce->name, len);
}

struct cache_entry *index_name_exists(struct index_state *istate, const char *name, int namelen, int icase)
{
unsigned int hash = hash_name(name, namelen);
struct cache_entry *ce;

lazy_init_name_hash(istate);
ce = lookup_hash(hash, &istate->name_hash);

while (ce) {
if (!(ce->ce_flags & CE_UNHASHED)) {
if (same_name(ce, name, namelen, icase))
return ce;
}
ce = ce->next;
}

/*
* When looking for a directory (trailing '/'), it might be a
* submodule or a directory. Despite submodules being directories,
* they are stored in the name hash without a closing slash.
* When ignore_case is 1, directories are stored in a separate hash
* table *with* their closing slash.
*
* The side effect of this storage technique is we have need to
* lookup the directory in a separate hash table, and if not found
* remove the slash from name and perform the lookup again without
* the slash. If a match is made, S_ISGITLINK(ce->mode) will be
* true.
*/
if (icase && name[namelen - 1] == '/') {
struct dir_entry *dir = find_dir_entry(istate, name, namelen);
if (dir && dir->nr)
return dir->ce;

ce = index_name_exists(istate, name, namelen - 1, icase);
if (ce && S_ISGITLINK(ce->ce_mode))
return ce;
}
return NULL;
}

static int free_dir_entry(void *entry, void *unused)
{
struct dir_entry *dir = entry;
while (dir) {
struct dir_entry *next = dir->next;
free(dir);
dir = next;
}
return 0;
}

void free_name_hash(struct index_state *istate)
{
if (!istate->name_hash_initialized)
return;
istate->name_hash_initialized = 0;
if (ignore_case)
/* free directory entries */
for_each_hash(&istate->dir_hash, free_dir_entry, NULL);

free_hash(&istate->name_hash);
free_hash(&istate->dir_hash);
}
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